1. Field of the Invention
The present invention relates to an image recording material which can be used as a planographic printing plate material. More particularly, it relates to a negative type image recording material for a planographic printing plate material which is usable for the so-called direct plate making and which is capable of directly making a printing plate using an infrared laser based on digital signals outputted from a computer or the like.
2. Description of the Related Art
As systems of direct plate making from digital data of computers, there have hitherto been proposed (1) systems using an electrophotographic method, (2) systems using photopolymerization wherein exposure is carried out using a laser emitting blue or green light, (3) systems formed by laminating a silver salt layer on a photosensitive resin, (4) systems formed by a silver salt diffusion-transfer method and the like.
However, in (1) a system using an electrophotographic method, image forming processes such as electrification, exposure, development and the like are complicated and, therefore, apparatus becomes complicated and large. In (2) a system using photopolymerization, since the printing plate is highly sensitive to blue or green light, it becomes difficult to handle the plate in an illuminated room. In methods (3) and (4), since a silver salt is used, those methods have a disadvantage in that processes such as development and the like become complicated and also waste solutions contain silver.
On the other hand, laser technology has advanced remarkably in recent years and, particularly, high output and small-sized solid-state lasers and semiconductor lasers which emit infrared-rays having wavelengths of 760 nm to 1200 nm are easily available. These lasers are very useful as a light source for recording when direct plate making is carried out from the digital data of computers and the like. However, since many practically useful photosensitive recording materials are sensitive to visible light having wavelengths of not greater than 760 nm, image recording cannot be performed with these infrared lasers. For this reason, there is a demand for a material which is recordable with an infrared laser.
As an image recording material which is recordable with such infrared laser, there is a recording material comprising an onium salt, a resol resin, a novolak resin and an infrared light absorbing agent described in U.S. Pat. No. 5,372,907 corresponding to Japanese Patent Application Laid-Open (JP-A) No. 7-20629. In addition, a recording material comprising an s-triazine substituted with a haloalkyl group, a resol resin and a novolak resin, and an infrared light absorbing agent is described in Japanese Patent Application Laid-Open (JP-A) No. 7-271029. However, plate materials using these image recording materials have a problem in that staining is produced on non-image parts upon image formation and printing after being stored for a long period of time at high temperatures.